That may depend on how you transfer the picture to the iPad.
If you do it via iTune "Sync", then the picture is modified, or "optimized for iPad".. hence, the picture may appear better.. or maybe the IPS screen could cause it to look better too..
But not sure why it shows only 1 colour.. I tested it..
On paper, it is supposed to support 24bit colour too like many monitors.. Maybe it depends on monitor calibration too.. or maybe due to Mac and Window PC's different gamma?
Any Mac users got tried? on calibrated and uncalibrated Mac systems..